1. Field of the Invention
The present invention relates to tumor associated antigens (TAA) and TAA peptides, to the use thereof, to the use of polynucleotides encoding same, and to the use of cells presenting same as anti-tumor vaccines. More particularly, the present invention relates to tumor associated antigen peptides derived from prostate specific G protein-coupled receptor (PSGR), six-transmembrane epithelial antigen of prostate (STEAP) and proteins encoded by polynucleotides overexpressed in colon carcinoma cells and the use of same for diagnosis and as anti-tumor vaccines to treat or inhibit the development of colon and prostate cancers, particularly carcinomas. More particularly, the present invention relates to tumor associated antigen peptides which are presentable to the immune system by HLA-A2 molecules.
2. Description of the Related Art
Local therapy such as surgical excision or ablation by radiation is a mainstay for the treatment of primary cancer and is curative for a percentage of patients. However, many malignancies will recur locally or at a distant site. Thus the prevention or cure of metastases remains a major focus in clinical oncology (Fidler et al., 1987). Although early detection followed by surgery provides good prognosis for a number of major cancer types, a large fraction of patients would need adjuvant therapy. Part of these patients will, with time, succumb to metastasis (Abeloff, 1996; Andriole, 1997; and Nseyo et al., 1997). Alternative approaches based on gene therapy and immunotherapy have been the focus of attention in the last years. One such approach is specific active immunotherapy (SAI; Kedar et al., 1995). The objective of SAI is to stimulate a tumor specific cytotoxic T lymphocytes (CTL) immune response that is capable of eliminating residual metastatic disease and induce a state of immunity to protect the patients from recurrent disease. The underlying assumption of SAI is that tumor cells express tumor antigens which are sufficiently distinct in structure or context to induce an effective CTL response (Urban et al., 1992). Although the validity of these assumptions was questioned, a number of studies in the last decade have demonstrated the rationale of SAI. In a landmark study, van Pel and Boon have shown that tumor associated antigens (TAAs) can be isolated and defined (Van Pel et al., 1982). Importantly, ex-vivo manipulations of “non-immunogenic” animal tumor cells can be used to elicit effective immune responses which will also recognize parental “non-immunogenic” tumor cells (Pardoll, 1993). Studies employing rodent tumor models with little intrinsic immunogenicity have shown that in genetically modified tumor cells transduced to express MHC class I, cytokines such as IL-1, IL-2, IL-4, IL-6, IL-7, IL-12, γIFN or GM-CSF or costimulatory molecules such as B7-1 or B7-2 were capable of preventing or causing regression of tumors or metastases (Qin et al., 1996). Although gene modified tumor vaccine (GMTV) clinical trials with improved retroviral vectors or other transfer methodologies are currently tested, it becomes clear that GMTV using autologous tumor cells might be limited by its complexity, high cost and ineffective gene transfer methodologies (Pardoll, 1996). One alternative approach would be vaccination with tumor associated antigens (TAAs) presented in an effective way to the patient's immune system, to induce antigen specific CTL (Boon et al., 1996).
Cytotoxic T lymphocytes (CTL), directed against peptides presented by MHC class I molecules, constitute powerful effectors of the immune system against tumors or infectious agents (Townsend et al., 1989). These peptides are usually 8-10 amino acids long with 2-3 primary anchor residues that interact with the MHC class I molecules and 2-3 amino acid residues which bind to the T cell receptor (Rammensee et al., 1993). Several methods have been employed to identify CTL epitopes. If the amino acid sequence of a protein antigen is known, like in the case of viral proteins, oncogenes, suppressor genes or growth factor receptors, overlapping peptides of 8-10 amino acids in length can be synthesized and screened as CTL targets (Feltkamp et al., 1993). CTL epitopes may also be identified subsequent to the search for MHC binding motifs in known proteins (Kast et al., 1994). If the tumor antigen is not known, isolation of the TAA peptides from total acid extract or from MHC class I molecules followed by HPLC fractionation steps and Edman sequencing (Mandelboim et al., 1994) or mass spectrometry (Cox et al., 1994) provide a direct way of identifying CTL epitopes. A synthetic combinatorial library approach, in which defined amino acids in two MHC anchor positions are fixed and all other positions are subgrouped for CTL screening has led to the description of novel EL4 TAA peptide mimotopes (Blake et al., 1996).
The most fruitful method, so far, designed by T. Boon and his colleagues is the genetic approach in which cDNA expression libraries are pool transfected into COS7 cells with the appropriate HLA and screened by CTL lines. This approach led to the discovery of several human melanoma and mouse mastocytoma antigens recognized by specific CTL (Boon et al., 1994). The first report of a phase I clinical trial with the synthetic MAGE3 melanoma peptide, restricted by HLA-A1, showed regression of cutaneous, subcutaneous and lung metastases in 3/6 patients (Marchand et al., 1995). Recently, two reports of clinical trials have shown that treatment of patients with a melanoma gp100 TAA peptide together with IL-2 resulted in significant tumor regression in 13/31 (42%) patients and that vaccination with defined peptides or total peptide extracts on autologous dendritic cells (DC) resulted in complete or partial cures (Rosenberg et al., 1998 and Nestlel et al., 1998). Regression of lung carcinoma established metastases or small established tumors was demonstrated in a murine model by peptide vaccination (Mandelboim et al., 1995 and Mayordomo et al., 1995). These observations suggest that TAA peptide vaccines may constitute a reasonable therapeutic modality in advanced cancer. In studies with murine tumors, CTL are induced in vivo by immunization with irradiated tumor cells, often gene modified by MHC class I; cytokine or costimulatory molecules like B7-1 or B7-2 genes (Mandelboim et al., 1994; Blake et al., 1996 and Fearon et al., 1990). In melanomas, CTL lines were mostly induced from peripheral blood mononuclear cells (PBMC) of patients or from tumor infiltrated lymphocytes (TIL, Boon et al., 1994 and Bakker et al., 1994). Yet, most metastatic tumors are non-immunogenic tumors and it is extremely difficult to derive CTL lines or clones from TIL or patient's PBL. Moreover, in vitro propagated CTL clones do not always represent dominant anti-tumor specificities but rather sporadic clones surviving culture conditions. Lately, a number of studies have compared the CTL repertoire of viral or other defined peptides, restricted by HLA-A2.1 in human PBL from HLA-A2.1 expressing patients to CTL induced in HLA-A2.1 transgenic mice. Good concordance between human HLA-A2.1 and murine transgenic HLA-A2.1 CTL repertoire was found, confirming the potential of such transgenics in identification of human CTL epitopes (Wentworth et al., 1996). Although vaccination with defined peptides of HLA transgenic mice shows an overlapping repertoire to human CTL, vaccination of such mice with multi-epitope proteins shows that murine H-2 restricted responses are dominant and obliterate, as a rule, cytolytic responses with direct recognition of human HLA (Barra et al., 1993). Thus, by combining classical HLA class I transgenesis with selective destruction of murine H-2, it is possible to derive useful mouse strains for the study of HLA class I restricted responses.
Murine H-2 knockout mice transgenic for a single human HLA seem to be a suitable model for induction of anti-tumor CTL. Classical β2 microglobulin knockout mice (β2m−/−) do not express H-2Kb or other non-classical class I molecules, yet they express low levels of H-2Db heavy chain in the absence of β2m. To derive fully H-2 knockout mice, Prof. F. Lemonnier (Pasteur Institute, Paris), prepared H-2Db−/− mice. These mice were crossed with β2m−/− mice and bred to derive homozygous β2m−/−, Db−/− mice that do not express any H-2 class I. These mice are practically depleted of CD8+ splenocytes, as well as other CD8+ cells. To reconstitute in these mice expression of a stable HLA-A2.1, expression of β2m is necessary. A construct containing a leader sequence, domains α1 and α2 of HLA-A2.1 and α3, transmembrane and cytoplasmic domains of H-2Db fused to human β2m (HhD) was prepared. The exchange of the α3 human domain by a murine domain in HhD is thought to improve the interaction of the class I molecule with CD8 molecules of the murine CTL (Vitiello et al., 1991). This HhD construct was transfected into RMA and RMA-S cells and shown to bind HLA-A2.1 restricted peptides. The HhD construct was used to produce transgenic mice in C57BL/6 recipients and positive founder mice were bred to the β2m−/−, Db−/− mice (Pascolo et al., 1997).
The β2m−/−, Db−/−, HhD−/+ heterozygous mice show reconstitution of CD8+ cells in the periphery relative to β2m−/− Db−/− mice. Moreover, preliminary data from Prof. Lemonnier's lab showed that CTL induced in HhD mice against influenza NP are directed to the same HLA-A2 dominant epitope as in the human repertoire. Homozygous HhD mice were derived and a colony was established in the Weizmann Institute of Science, Israel.
The identification of genes encoding unique tumor associated antigens (TAAs) has facilitated the development of novel immunotherapeutic strategies in cancer patients. Clinical investigations have focused on targeting these cancer antigens for the generation of anti-tumor T-cell responses. TAA epitopes come from differentiation antigens, from embryonal reexpressed or overexpressed proteins, from mutated proteins and from viral proteins in viral-associated tumors (Eisenbach et al., 2000 and Offringa et al., 2000).
CD8+ cells, which recognize MHC class I molecules bearing oligopeptides that are generated in the cell cytosol, are a major arm of the cellular immune response against viral infections, intracellular bacteria and various types of malignancies. Upon appropriate vaccination, these cytotoxic T lymphocytes (CTL) constitute powerful effectors against tumors that present on their cell surface MHC class I molecules tumor associated antigenic (TAA) peptides (Eisenbach et al., 2000)
The human tumor antigens are currently categorized according to their function or origin: (a) Cancer-Testes antigens—these antigens are expressed in tumors but not in normal tissues with the exception of the testis; (b) Differentiation antigens—these antigens originally identified for melanoma and consist of several “self” antigens of normal melanocytes, like Melan A, gp100 and others. HLA restricted peptides of these antigens are major targets for immunotherapy against melanoma; (c) Mutational antigens—point mutations in normal genes that are frequent in many kinds of tumors like mutated p53 and ras oncoproteins, were shown to generate TAA peptides, which upon proper stimulation induce strong anti-tumor CTL responses; (d) Overexpressed “self” antigens—many tumors constitutively overexpress self genes. Although strong immune reactions against this type of antigens might result in the destruction of normal tissues, experiences with peptide immunization in patients as well as numerous animal studies have not shown prominent toxicity concerns; (e) Viral antigens—in some cervical and anal malignancies, for example, proteins of HPV are expressed in tight association with tumors and, therefore, can be used as targets for the immune system (Offringa et al., 2000).
Thus far, little is known about possible natural target antigens for CTL in colo-rectal carcinoma patients. The few potential targets that were identified belong to the overexpressed genes, such as: her-2/neu, CEA and the recent Ep-CAM discovered by applying SEREX technology (Melief et al., 2000). Despite the fact that these antigens show natural CTL responses in patients, there is a strong need to expand the armory against colon carcinoma by discovering new TAAs (Nagorsen et al., 2000).
Prostate cancer (CaP) is increasingly recognized as a major health problem; it is the most frequently diagnosed cancer in the Western male population and the second leading cause of cancer related death in this population. Although locally confined disease is treatable, recurrent and metastasized CaP is essentially incurable. Androgen ablation therapy may palliate advanced disease, as long as prostate cells are androgen-responsive. However, the majority of patients inevitably progress to incurable, androgen-independent disease (Hubert et al., 1999). Current efforts are now directed towards developments of immunotherapy based strategies for the treatment of CaP.
WO 00/06723, which is applicants' own published PCT International application, discloses tumor associated antigen (TAA) peptides derived from uroplakin Ia, Ib, II and III, prostate specific antigen (PSA), prostate acid phosphatase (PAP), prostate specific membrane antigen (PSMA), BA=46 (lactadherin), mucin (MUC-1), and teratocarcinoma-derived growth factor (CRIPTO-1) and the use of these TAA peptides in an anti-tumor vaccine to prevent or cure bladder, prostate, breast or other cancers, particularly carcinomas.
Citation of any document herein is not intended as an admission that such document is pertinent prior art, or considered material to the patentability of any claim of the present application. Any statement as to content or a date of any document is based on the information available to applicant at the time of filing and does not constitute an admission as to the correctness of such a statement.